Lead free, composite polymer based bullet and method of manufacturing

ABSTRACT

A lead-free, composite polymer based bullet and cartridge case and methods of manufacturing the same, wherein the composite polymer material includes a tungsten metal powder, nylon 6/6, nylon 6, short glass fibers, as well as additives and stabilizers. The cartridge case includes a lip lock configured to matingly engage a cannelure formed along an outer circumferential surface of the bullet. The cartridge case also includes resilient walls wherein the case may snap fit onto the bullet. The bullet and cartridge case may be formed in a single step process by injection molding or a two step process including injection molding and a welding process.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. patent application Ser. No.10/695,158, filed Oct. 29, 2003 now abandoned, which claims priortybenefit to U.S. Provisional Application No. 60/421,782, filed Oct. 29,2002. The disclosures of the prior applications are hereby incorporatedby reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to bullets/projectiles (hereinafterreferred to as bullets) and cartridge cases. More particularly, thepresent invention relates to lead free, composite polymer based bulletsand cartridge cases, and a method of manufacturing the same.

2. Description of Related Art

It is well known in the industry to manufacture bullets andcorresponding cartridge cases from either brass or steel. Typically,industry design calls for materials that are strong enough to withstandextreme operating pressures and which can be formed into a cartridgecase to hold the bullet, while simultaneously resist rupturing duringthe firing process.

Conventional ammunition typically includes four basic components, thatis, the bullet, the cartridge case holding the bullet therein, apropellant used to push the bullet down the barrel at predeterminedvelocities, and a primer, which provides the spark needed to ignite thepowder which sets the bullet in motion down the barrel.

The cartridge case is typically formed from brass and is configured tohold the bullet therein to create a predetermined resistance, which isknown in the industry as bullet pull. The cartridge case is alsodesigned to contain the propellant media as well as the primer.

The bullet is configured to fit within an open end or mouth of thecartridge case and conventionally includes a groove (hereinafterreferred to as a cannelure) formed in the mid section of the bullet toaccept a crimping action imparted to the metallic cartridge casetherein. When the crimped portion of the cartridge case holds the bulletby locking into the cannelure, a bullet pull value is providedrepresenting a predetermined tension at which the cartridge case holdsthe bullet. The bullet pull value, in effect, assists imparting aregulated pressure and velocity to the bullet when the bullet leaves thecartridge case and travels down the barrel of a gun.

Furthermore, the bullet is typically manufactured from a soft material,such as, for example only, lead, wherein the bullet accepts the mouth ofthe cartridge being crimped to any portion of the bullet to hold thebullet in place in the cartridge case, even though the cartridge case iscrimped to the cannelure of the bullet.

The propellant is typically a solid chemical compound in powder formcommonly referred to as smokeless powder. Propellants are selected suchthat when confined within the cartridge case, the propellant burns at aknown and predictably rapid rate to produce the desired expanding gases.As discussed above, the expanding gases of the propellant provide theenergy force which launches the bullet from the grasp of the cartridgecase and propels the bullet down the barrel of the gun at a known andrelatively high velocity.

The primer is the smallest of the four basic components used to formconventional ammunition. As discussed above, primers provide the sparkneeded to ignite the powder which sets the bullet in motion down thebarrel. The primer includes a relatively small metal cup which containsa priming mixture, foil paper, and relatively small metal post, commonlyreferred to as an anvil.

When a firing pin of a gun or firearm strikes a casing of the primer,the anvil is crushed to ignite the priming mixture contained in themetal cup of the primer. Typically, the primer mixture is an explosivelead styphnate blended with non-corrosive fuels and oxidizers whichburns through a flash hole formed in the rear area of the cartridge caseand ignites the propellant stored in the cartridge case. In addition toigniting the propellant, the primer produces an initial pressure tosupport the burning propellant and seals the rear of the cartridge caseto prevent high-pressure gases from escaping rearward. It should benoted that it is well known in the industry to manufacture primers inseveral different sizes and from different mixtures, each of whichaffects ignition differently.

The cartridge case, which is typically metallic, acts as a payloaddelivery vessel and can have several body shapes and headconfigurations, depending on the caliber of the ammunition. Despite thedifferent body shapes and head configurations, all cartridge cases havea feature used to guide the cartridge case, with a bullet held therein,into the chamber of the gun or firearm.

The primary objective of the cartridge case is to hold the bullet,primer, and propellant therein until the gun is fired. Upon firing ofthe gun, the cartridge case seals the chamber to prevent the hot gasesfrom escaping the chamber in a rearward direction and harming theshooter. The empty cartridge case is extracted manually or with theassistance of gas or recoil from the chamber once the gun is fired.

There are three common cartridge case designs that are well known in theindustry. In particular, a bottleneck cartridge case 10 shown in FIG. 1is used with rifles. A straight inner walled cartridge case 20 shown inFIG. 2 has inner walls of the cartridge case that are substantiallyparallel with a longitudinal axis of the case, which is commonly usedwith pistols. A tapered straight inner walled cartridge case 30 shown inFIG. 3 has inner walls that are oblique or not parallel relative to thelongitudinal axis of the case and is commonly used with revolvers.

As shown in FIG. 1, the bottleneck cartridge case 10 has a body 11formed with a shoulder 12 that tapers into a neck 13 having a mouth at afirst end. A primer holding chamber 15 is formed at a second end of thebody opposite the first end. A web area 16 separates a main cartridgecase holding chamber 17, which contains a propellant, from the primerholding chamber 15, which communicate with each other via a flash holechannel 18 formed in the web area 16. An exterior circumferential regionof the rear end of the cartridge case includes an extraction groove 19 aand a rim 19 b.

As can be seen in FIG. 2, the straight inner walled cartridge case 20does not include a shoulder that tapers to a neck 23 at the first end ofthe cartridge case 20. Furthermore, the straight inner walled cartridgecase 20 does not have a rim significantly larger than a case diameterD₂₀ and is commonly referred to as a rimless case in the industry.Likewise, the tapered straight wall cartridge case 30 shown in FIG. 3Adiffers from the cartridge case 20 shown in FIG. 2 as it has interiortapered walls and a rim 39 b larger than a case diameter D₃₀.

FIG. 3B is an enlarged view of a lip lock 32 provided in the vicinity ofthe mouth 34 of the cartridge case 30. The lip lock 32 includes a first,generally straight portion 32 a, which is orthogonal to a longitudinalaxis of the case 30; a second, generally straight portion 32 b, which isparallel to the longitudinal axis of the case 30 and orthogonal to thefirst straight portion 32 a; and a slanted portion 32 c, which isoblique relative to the longitudinal axis of the cartridge case 30 andboth straight portions 32 a and 32 b. The lip lock 32 is used tosecurely grip a bullet (not shown).

Typically, manufacturers must take as many as twenty three (23) steps tomanufacture a brass cartridge case from a rolled strip of brassmaterial. During loading, which is the step where the cartridge case isloaded with the powder and bullet, the brass cartridge case is crimpedto the bullet so that the bullet is held therein. It is well understoodthat crimping is necessary to assist in creating the pressure needed forsatisfactory ballistic performance.

Ballistic performance is a set of measurable events resulting from thecombination of a particular bullet weight placed over a particularpropellant charge to be ignited by a priming method of predeterminedsize that establishes the pressure build up needed to propel the bulletat a desired velocity.

As shown in the schematic diagram of FIG. 4, case walls 41 a and 41 b ofthe brass cartridge cases 40 are typically crimped at a mouth 44 ontothe bullet B to hold the bullet B in place. The contact surface is thewall thickness of the brass cartridge case 40 at the point the cartridgecase 40 is crimped.

Alternatively, the cartridge case 50 may be tapered from a rear end 51to the mouth 54, as shown in FIG. 5, so as to create a press fit P atthe mouth 54 of the case 50, which causes the bullet B to be held inplace over a larger bearing surface.

In yet another alternative, adhesives may be used to hold the cartridgecase and bullet assembly together to assist in providing a desiredpressure. Some commercial, law enforcement, and military firearmsammunitions are assembled with adhesives to provide an increasedpressure where a simple crimping step is not sufficient.

In the late 1990's it was reported that the military would begin the useof so-called green bullets. Supposedly, such green bullets would be madeof high-density materials, such as tungsten, mixed with lightermaterials, such as tin and zinc. It was also reported thattungsten-nylon cores could be used. However, no specific range ofingredients was ever provided. It should be noted that the green bulletswere fabricated with copper jackets. See Mikko, Assoc. of Firearm andTool Mark Exam. Journ., vol. 31, No. 4, Fall 1999; USA Today, “‘Green’Army bullets to get the lead out,” and Environmental Update, Fall 1999.

Several patents for green bullets have been issued.

For example, WO 88/09476 to Booth discloses a bullet made of materialshaving a specific gravity of 3 to 7, a matrix of plastic material, suchas nylon 6 or nylon 6/6, and a filler of a finely divided metal, such ascopper, bronze or tungsten. In the preferred compositions, Nylon isincorporated in an amount of 8% or 11% by weight. The filler material ispresent in essentially the remainder amount. Either one of the nylon 6/6or nylon 6 is explained as being used in amounts of up to 20% by weight.Booth does not disclose using both nylon materials together in the samebullet.

U.S. Pat. No. 5,616,642 to West et al. discloses a bullet containing ahigh density powder, such as copper, tungsten, bismuth, ceramic orstainless steel, in an amount of at least 85%, dispersed in a polyestermatrix, such as polybutylene terephthalate or polyethyleneterephthalate.

U.S. Pat. No. 6,048,379 to Bray et al. discloses a bullet made oftungsten, a fiber, such as stainless steel, copper, aluminum, nylon,Kevlar, Spectra, nickel, glass or carbon, and a binder material, such asnylon 12 or a polyester elastomer. Bray et al. indicate nylon 6/6 andnylon 6 are resins that are not suitable as binders. See column 10,lines 18–19.

U.S. Pat. No. 6,257,149 to Cesaroni discloses a bullet having a coremade of a polymer, such as ethylene/methacrylic acid copolymer ionomers,polyetherester elastomers or polyamides, such as nylon 11 or nylon 12,and a jacket made of copper, nylon 6/6, nylon 6/12, nylon 4/12, flexiblenylon, nylon 6 or nylon 11.

As stated above, the test for all methods of holding the bullet within acartridge case is commonly known as bullet pull. The Sporting Arms andAmmunition Manufactures Institute (hereinafter referred to as“S.A.A.M.I.”) established a bullet pull for all calibers that creates adesired pressure to deliver the desired ballistics. The United StatesMilitary has also established bullet pull specifications that achievethe products desired ballistic performance.

SUMMARY OF THE INVENTION

It is an aspect of the present invention to provide a bullet, acartridge case, and method of manufacturing the same that overcome thedrawbacks of the conventional brass or lead bullets, cartridge case, andlaborious, yet required, methods of manufacturing given the materialcompositions of the same.

In particular, it is an aspect of the present invention to provide alead free, composite polymeric bullet and cartridge case, and method ofmanufacturing the same by injection molding requiring one or two steps,dependent on the cartridge caliber, to manufacture the cartridge case asopposed to the twenty three steps commonly needed to prepare theconventional brass cartridge cases. Furthermore, the present inventionalso manufactures bullets in a single step by injection molding, asopposed to as many as six (6) steps needed to manufacture theconventional lead based bullets.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects and features of the present invention will be betterunderstood from the following description, with reference to theaccompanying drawings, wherein:

FIG. 1 is a cross sectional view of a conventional bottleneck cartridgecase used with rifles;

FIG. 2 is a cross sectional view of a straight walled rimless cartridgecase used with pistols;

FIG. 3A is a cross sectional view of a tapered straight walled cartridgecase having a rim and used with revolvers;

FIG. 3B is an enlarged view of a lip lock provided near a mouth of thecartridge case illustrated in FIG. 3;

FIG. 4 is a schematic diagram illustrating how a conventional cartridgecase is bent in the mouth region to hold the bullet therein;

FIG. 5 is a schematic diagram illustrating how a conventional cartridgecase is tapered from the base of the case to the mouth region to pressfit the case onto the bullet;

FIG. 6 is a cross sectional view of a cartridge case according to afirst embodiment of the present invention;

FIG. 7 is an enlarged view of the lip lock of the cartridge case shownin FIG. 6;

FIG. 8 is a cross sectional view of the cartridge case shown in FIG. 6holding a corresponding caliber bullet;

FIG. 9 is a cross sectional view of a cartridge case according to asecond embodiment of the present invention;

FIG. 10 is a an enlarged view of the lip lock of the cartridge caseshown in FIG. 9;

FIG. 11 is a cross sectional view of the cartridge case shown in FIG. 9holding a corresponding caliber bullet;

FIG. 12 is a table of a ballistic chart; and

FIGS. 13A–C illustrate a method for producing an all-polymer injectionmolded cartridge case.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides a cartridge case body strong enough towithstand gas pressures that equal or surpass the strength of brasscartridge cases under certain conditions. Furthermore, the presentinvention provides a lead free, composite polymer based bullet having aspecific gravity high enough to perform as well as if not better thanconventional lead based bullets.

FIG. 6 illustrates a first embodiment of the invention. In particular, acartridge case 60 for holding a 0.45 caliber bullet therein is shown.The cartridge case satisfies S.A.A.M.I. requirements for 0.45 caliberammunition.

For example, the cartridge case 60 has a front end that holds the bullet(not shown) and a rear end that holds the primer. A length I of thecartridge case 60 from a front end face 61 to a rear end face 62 rangesfrom about 0.888 in. to 0.898 in., and preferably is about 0.894 in. Anouter diameter D_(M) of the cartridge case 60 at a mouth 63 is about0.467 in. to 0.473 in., and preferably is about 0.470 in. and an outerdiameter D_(P) at a rear end 64 of the cartridge case 60 is about 0.469in. to 0.476 in. and preferably is about 0.471 in.

The rear end 64 of the cartridge case 60 has a groove 65 formed thereinwith a thickness G_(T) that ranges from about 0.036 in. to 0.39 in., andpreferably is about 0.38 in. and a depth G_(D) that ranges from about0.037 in. to 0.043 in., and preferably is about 0.040 in. (see FIG. 8)The groove 65 defines a rim 66 at the most rearward point of thecartridge case 60, wherein the rim 66 has an outer diameter D_(R) thatranges between about 0.470 in. and 0.476 in., and preferably is about0.474 in. and a width W_(R) that ranges between about 0.039 in. and0.049 in., and preferably is about 0.045 in.

Radially inward relative to the groove 65 is a primer holding chamber66, which has an outer diameter D_(PC) that ranges from about 0.203 in.to 0.210 in., and is preferably about 0.207 in. and a depth dpc thatranges from about 0.115 in. to 0.120 in., and preferably is about 0.117in.

A bullet holding chamber 67 and the primer holding chamber 66 define aweb 68 in the portion of a cartridge case body 69 therebetween, whereinthe web 68 has a thickness W_(T) that ranges between about 0.047 in. and0.100 in., and preferably is about 0.050 in. The primer holding chamber66 communicates with the bullet holding chamber 67 via a flash hole 70formed in the web 68, wherein the flash hole 70 has an outer diameterD_(FH) that ranges between about 0.077 in. to 0.83 in., and preferablyis about 0.80 in.

As shown in FIG. 6, the cartridge case 60 has a substantiallycylindrical configuration with inner walls 71, 71 that taper from a rearend 72 of the bullet chamber 67 toward the mouth 63 located at the frontend of the bullet chamber 67. The taper of the cartridge case innerwalls 71, 71 transitions to walls 73, 73 that are parallel relative to alongitudinal axis x—x of the cartridge case 60. The transition occurs ata region of the case that is intermediate relative to the rear and frontends of the bullet chamber 67 and is referred to as a blend point 74.

As shown in FIG. 6, a lip lock 75 is located at the most forward pointof the cartridge case body 69 to define the mouth 63 of the cartridgecase 60. The lip lock 75 holds the bullet (not shown) in the cartridgecase 60.

FIG. 7 shows an enlarged view of the lip lock 75, which has a baseportion 75 a that coincides with the outer surface of the cartridge caseand is about 0.010 in. to 0.030 in. in length, and preferably is about0.020 in. in length. The lip lock 75 has a unique configuration which isvariable from an asymmetrical shape having a tapered rearward portion(as shown) to various symmetrical configurations depending on thedesired bullet holding requirements. A taper portion 75 b of the liplock 75 has a thickness that is about 0.010 in. and a width that rangesfrom about 0.020 in. at the widest portion to a width that correspondsto the length of the engaging portion. An engaging portion 75 c of thelip lock 75 has a length leg ranging from about 0.008 in. to 0.012 in.,and preferably is about 0.010 in.

It should be noted that the engaging portion 75 c of the lip lock 75should have a length leg that does not exceed the overall width of acannelure formed in the bullet (not shown), which will be describedbelow, such that the engaging portion 75 c of the lip lock 75 is able tofit within the bullet lip lock cannelure. Furthermore, although notrequired, it is preferable that the base portion 75 a of the lip lock 75is parallel relative to the engaging portion 75 c, but it is within thescope of this invention to arrange the engaging portion 75 c to beoblique relative to the base portion 75 a.

The cartridge case 60 and bullet are manufactured by an injectionmolding process from a composite polymer by feeding the polymer throughan injection molding apparatus. Because the cartridge case 60 ismanufactured from a composite polymer, the walls of the cartridge case60 from the mouth 63 to the blend 74 are able to be bent either radiallyinward toward the longitudinal axis x—x of the case or radially outwardaway from the longitudinal axis x—x. The flexibility of the case wallspermit the mouth 63 to be temporarily expanded to receive thecorresponding bullet, which is also manufactured from a compositepolymer that may or may not be the same as the composite polymer used tomanufacture the cartridge case. Properly prepared with the correctcorresponding groove, conventional lead or jacketed bullets can be usedwith the polymer cartridge case design described herein.

Once the mouth 63 is expanded, the corresponding bullet B is insertedtherein. It should be noted that the bullet B has an outer diameterD_(B) that ranges between 0.450 in. to 0.453 in., and preferably is0.451 in. (see FIG. 6) Furthermore, the bullet B (FIG. 8) has acannelure 80 formed on an outer circumferential surface at a locationthat permits the engaging portion 75 c of the lip lock 75 to be insertedtherein and wherein the bullet B is not inserted beyond the blend 74 onthe inner walls 71, 71 of the case body 69.

Accordingly, the bullet is inserted into the bullet holding chamber 67of the cartridge case 60 by slightly expanding the mouth 63 until thebullet cannelure 80 coincides with the engaging portion 75 c of the liplock 75. The lip lock 75 is then permitted to snap back to an originalposition wherein the engaging portion 75 c of the lip lock 75 matinglyengages the cannelure 80 of the bullet B. See FIG. 8. The lip lock 75provides enough resistance to provide the required bullet pull value ofapproximately 5 to 20 pounds, which is greatly reduced from conventionalbullet pull values for brass cartridge cases, which are approximately 35to 65 pounds. U.S. Military Specifications require a higher bullet pullin some cases to assure that certain Legacy Weapons Systems will fullyfunction properly. In these cases, the bullet pull of this invention canbe increased to accommodate any U.S. Military Weapon Systems.

The lip lock 75 also prevents creeping of the bullet. Creep occurs whena bullet moves forward in its case due to recoil generated by the firingof adjacent cartridges. In a semi-automatic pistol, creep can causecartridges to jam in the magazine and/or prevent proper feeding into thechamber due to excessive overall length, which would render the pistolinoperable.

As shown in FIG. 8, the overall length 160 of the cartridge case 60 andbullet B held therein ranges from about 1.190 in. to 1.270 in. and ispreferably about 1.263 in. in length. Furthermore, when the firearm isfired, the lip lock 75 permits the smooth release of the bullet B, whichenhances the accuracy of the firearm.

The present invention is not limited to the above-described caliber andis believed to be applicable to other calibers as well. For example,FIGS. 9–11 show a second embodiment of the invention, and in particular,a cartridge case 100 for holding a 38 special caliber bullet. Thecartridge case 100 satisfies S.A.A.M.I. requirements for 38 specialcaliber ammunition.

A length I′ of the cartridge case 100 from a front end face 161 to arear end face 162 ranges from about 1.135 in. to 1.155 in., andpreferably is about 1.154 in. An outer diameter D₁₀₀ of the cartridgecase 100 at a mouth 163 is about 0.372 in. to 0.379 in., and preferablyis about 0.374 in. and an outer diameter D_(P2) at a primer end is about0.372 in. to 0.376 in. and preferably is about 0.374 in.

A rear end 164 of the cartridge case 100 has a rim 166 formed thereon,wherein the rim 166 has an outer diameter D_(R2) that ranges betweenabout 0.428 in. and 0.440 in., and preferably is about 0.433 in. and awidth W_(R2) that ranges between about 0.048 in. and 0.059 in., andpreferably is about 0.056 in.

Radially inward relative to a groove 165 is a primer holding chamber166, which has an outer diameter D_(PC2) that ranges from about 0.168in. to 0.175 in., and is preferably about 0.171 in. and a depth thatranges from about 0.115 in. to 0.120 in., and preferably is about 0.117in.

A bullet holding chamber 167 and the primer holding chamber 166 define aweb 168 in the portion of the cartridge case body therebetween, whereinthe web 168 has a thickness that ranges between about 0.047 in. and0.100 in., and preferably is about 0.050 in. The primer holding chamber166 communicates with the bullet holding chamber 167 via a flash hole170 formed in the web 168. The flash hole 170 has an outer diameterD_(FH2) that ranges between about 0.077 in. to 0.83 in., and preferablyis about 0.80 in. (see FIG. 11)

As shown in FIG. 9, the cartridge case 100 has a substantiallycylindrical configuration with inner walls 171 that taper from a rearend 172 of the bullet holding chamber 167 toward the mouth 163 locatedat the front end of the case. The taper of the cartridge case innerwalls 171 transitions to walls that are parallel relative to thelongitudinal axis of the cartridge case 100. The transition occurs at aregion of the case intermediate relative to the rear end 172 and mouth163 of the case 100 and is referred to as a blend point 174.

As shown in FIG. 9, a lip lock 175 is located at the most forward pointof the cartridge case body and defines the mouth 163 of the cartridgecase 100. The lip lock 175 holds the bullets in the cartridge case 100.The lip lock 175 also prevents creeping of the bullets. Creep occurswhen the bullet S moves forward in the case 100 due to recoil caused byfiring of adjacent cartridges. In a revolver, creep will allow thebullet to protrude out of the cylinder, preventing its rotation (causinga jam), thus rendering the firearm inoperable.

FIG. 10 shows an enlarged view of the lip lock 175, which has a baseportion 175 a that coincides with the outer surface of the cartridgecase 100 and is about 0.018 in. to 0.022 in. in length, and preferablyis about 0.020 in. in length. The lip lock 175 has a taper portion 175 bthat tapers from the base portion 175 a to an engaging portion 175 c,wherein the taper portion 175 b has a thickness that is about 0.010 in.and a width that ranges from about 0.020 in. at the widest portion to awidth that corresponds to the length of the engaging portion 175 c. Theengaging portion 175 c has a length ranging from about 0.008 in. to0.012 in., and preferably is about 0.010 in.

Once the mouth 163 is expanded, the corresponding bullet S is insertedtherein. It should be noted that the bullet S has an outer diameter thatranges between about 0.355 in. to 0.359 in., and preferably is about0.357 in. Furthermore, the bullet S has a cannelure 180 formed on anouter circumferential surface at a location that permits the engagingportion 175 c of the lip lock 175 to be inserted therein.

Accordingly, the bullet S is inserted into the bullet holding chamber167 until the bullet cannelure 180 coincides with the engaging portion175 c of the lip lock 175. The lip lock 175 is then permitted to snapback to an original position wherein the engaging portion 175 c of thelip lock 175 matingly engages the bullet cannelure 180. (See FIG. 11)The lip lock 175 provides enough resistance to provide a bullet pull ofabout 5 to 20 pounds which is greatly reduced from conventional bulletpull values for brass cartridge cases, which is about 35 pounds. Anoverall length I₁₀₀ of the cartridge case 100 and bullet S held thereinranges from about 1.400 in. to 1.550 in. and is preferably about 1.531in. in length. Furthermore, when the firearm is fired, the lip lock 175permits the smooth release of the bullet S, which enhances the accuracyof the firearm.

As stated above, the cartridge case and bullet are manufactured byfeeding a composite polymer through an injection molding machine intomolds configured to the particular geometric shapes of the case andcaliber of bullet, respectively. In other words, the entire and completecartridge case is manufactured or molded in a single operation.Furthermore, the entire and complete bullet is manufactured or molded ina single operation. The dimensions for the molds are selected to allowthe proper shrinkage of the composite polymer material to achieve thedesired specifications and/or caliber. As shown in the table of FIG. 12,the cartridge case is strong enough to provide the same pressureretention benefits as brass cartridge cases, and when the samepropellant is used, the lead free, composite polymer cartridge case ofthe present invention delivers the same velocities as brass cartridgecases, but at a substantially lower pressure curve. Also, as statedabove, compared to conventional brass case cartridges, the lead free,composite polymer cartridge case of the present invention providesbullet pull values that are 700% to 1400% less.

A first embodiment of the lead free, composite polymer material issuitable for the bullet. The polymer material includes, by weight, atungsten metal powder in the range of about 50–96%, preferably about60–95%, and most preferably about 70–90%, of the overall composition ofthe polymer material. It is most suitable that the tungsten metal powderbe present in at least 70% by weight. The polymer material also includesabout 0.5–15%, preferably about 1–12%, and most preferably about 2–9% byweight, of nylon 6/6, about 0.5–15%, preferably about 1–12%, and mostpreferably about 2–9% by weight, of nylon 6, and about 0.5–15%,preferably about 1–12%, and most preferably about 2–9% by weight, ofglass fibers. It is most suitable that each of these ingredients beincluded in amounts less than 10% by weight.

The polymer material according to the first embodiment preferably has aspecific gravity of 3–10, more preferably 6–9, and most preferably7.5–8.5. Preferably, the polymer material has a specific gravity whichpermits the molded bullet to provide a user with a point of aim that iscomparable to that of the conventional lead products. A bullet formed inaccordance with the present invention is environmentally friendly as itdoes not have any lead, performs ballistically similar to conventionalbullets, has a lower weight while using the same firearm holdcharacteristics, and can be produced at a substantially lowermanufacturing cost. Furthermore, the composite polymer material of thefirst embodiment preferably encapsulates the tungsten powder such thatthe composite polymer bullet does not wear down the barrel of thefirearm, which results in a longer life for the firearm.

The properties of the selected polymer material provide severaladvantages over the conventionally used brass and lead materials usedfor cartridge cases and bullets, respectively. For example, the polymermaterial provides a way for the cartridge case to hold the bullet thatreplaces crimping and eliminates a need to use adhesives in cases whereadhesives are required to provide the proper bullet pull properties whenusing brass cases. The unique lip lock design permits the cartridge caseto be snapped into the corresponding cannelure of the bullet.

Brass cartridge cases tend to form to the chamber walls when fired. Incontrast, the composite polymer cartridge case of the present inventionflexes during firing, but the material memory returns the cartridge caseto its original dimensions. Accordingly, the combination of thecomposite polymer material returning to its original dimension afterfiring, the lubricity of the polymer aid extraction in contrast tobrass, which ultimately inhibits extraction.

FIGS. 13A–C illustrate a method for producing an all-polymer, injectionmolded bottleneck cartridge case 200, wherein FIG. 13A illustrates abase 210, FIG. 13B illustrates a case 230, and FIG. 13C illustrates thecase 200 after assembly. The bottleneck shaped case is produced bymolding two separate parts, i.e., a case body 231 having a bottleneckconfiguration, and a base 210. The base 210 includes a rim 211 definingan extractor groove 212 having a ramp 213. A web 214 defines a flashhole 215 therethrough, wherein the flash hole 215 leads to a primerholding chamber 216.

The base 210 and case 230 are welded together in a secondary productionoperation. In order to achieve a strong weld, the base 210 and case 230must have a weld joint profile 216 and 232, respectively, molded intoeach of the two parts. The weld joint profiles are designed toaccommodate a welding process, which can include ultrasonic, spin orlaser welding. The welding procedure will be dictated by the choice ofpolymer material for the cartridge being manufactured. An importantdesign feature of the base 210 is the thickness of the web 214. In sometypes of firearms, the chamber does not fully support the base end ofthe cartridge case. In order to maximize the strength of the base inthis area, the flash hole channel of the present invention can beextended by making the web 214 relatively wider. Consequently, such adesign allows the explosive force of the primer and gunpowder ignitionto take place in the area of the chamber where the case is fullysupported.

Many modifications may be made to adapt the teachings of this inventionto particular situations or materials without departing from the scopethereof. Therefore, this invention should not be limited to theparticular embodiments disclosed herein, but includes all embodimentswithin the spirit and scope of the disclosure.

1. A lead-free bullet, comprising: a body made from a composite polymermaterial and having a front end and a rear end; a cannelure formed on anouter circumferential surface of the body intermediate the front andrear ends of the body, wherein the composite polymer material includes atungsten metal powder, nylon 6/6, nylon 6, and glass fibers; and aspecific gravity in a range of 3–10.
 2. The bullet according to claim 1,wherein the tungsten metal powder is 50%–96% of a weight of the bulletbody, the nylon 6/6 is 0.5% –15% of the weight of the bullet body, thenylon 6 is 0.5%–15% of the weight of the bullet body, and wherein theglass fibers are 0.5%–15% of the weight of the bullet body.
 3. Thebullet according to claim 2, wherein the tungsten metal powder is60%–95% of the weight of the bullet body, the nylon 6/6 is 1.0%–12% ofthe weight of the bullet body, the nylon 6 is 1.0%–12% of the weight ofthe bullet body, and wherein the glass fibers are 1.0%–12% of the weightof the bullet body.
 4. The bullet according to claim 3, wherein thetungsten metal powder is 70%–90% of the weight of the bullet body, thenylon 6/6 is 2.0%–9.0% of the weight of the bullet body, the nylon 6 is2.0%–9.0% of the weight of the bullet body, and wherein the glass fibersare 2.0%–9.0% of the weight of the bullet body.
 5. The bullet accordingto claim 1, wherein the specific gravity of the bullet is in the rangeof 6–9.
 6. The bullet according to claim 5, wherein the specific gravityof the bullet is in the range of 7.5–8.5.
 7. The bullet according toclaim 1, wherein the tungsten metal power is encapsulated in thecomposite polymer material.
 8. A method for manufacturing a lead-freebullet having a body made from a composite polymer material includingtungsten metal powder, nylon 6/6, nylon 6, and glass fibers, the methodcomprising the following steps: providing a mold configured to apredetermined caliber bullet; and feeding the composite polymer materialthrough an injection molding apparatus into the mold.